Composition for detonators



Patented Dec. 19, 1922.

team

COMPANY, OF WILMINGTON, DELAWARE, A

CORPORATION OF DELAWARE.

COMPOSITION FOR DETONATORS.

No Drawings.

To all whom it may concern:

Beit known that I, BENNETT GROTTA, a citizen of the United States, residing at Tamaqua, inthe county of Schuylkill and State of Pennsylvania, have invented certain new and useful Improvements in Compositions for Detonators, of which the following is a specification.

My invention relates to improvements to that class of detonators which contain a heavy metal azide as a whole or as a part of the charge.

For many years efforts have been made to effect improvements in detonators, by substituting some ingredient, either wholly or partially, for fulminate of mercury, the latter compound having been the chief initiating explosive of commercial importance since its discovery.

Fulminate of mercury is superior to all known commercially possible detonating explosives in one respect, in that detonation is assured, either by 'the spit of a fuse or other means of ignition, or by moderate percussion. On the other hand, fulminate of mercury exhibits several undesirable properties: (1) It is easily affected by moisture, a fraction of one percent of water content being suflicient to destroy its detonating value. (2) Its true detonating value is greatly diminished when compressed to high densities as is often times inevitable in the modern methods of manufacturing detonators. It has a relatively low brisance which renders necessary the use of an inner -capsule or re-inforced shell when it is desired to use fulminate of mercury :as a priming charge in the T. N. T., tetryl, or other nitrocompound types of detonators; a fact which is well known to all who are conversant in this branch of the explosives industry. (4) Due to the corrosive action of fulminate of mercury the number of metals or alloys which are suitable for detonator casings is greatly restricted. In contrast with fulminate of mercury there is another group of initiating explosives, namely, the heavy metal azides, which have several properties that are directly the reverse of those of fulminate of mercury. The azides are salts of hydrazoic acid which were discovered and, according to literature, were proposed as substitutes for or detonating value Application filed November 25, 1921. Serial No. 517,661.

fulminate of mercury before the year 1900. These compounds are scarcely affected by moisture or over-pressing and they possess muchgreater brisance or detonating value than fulminate of mercury.

On the other hand, the azides, especially lead azide which has been recognized as the only azide of commercial importance, has the disadvantage of not being easily ignited. As was stated above, fulminate of mercury is ignited with certainty by the spit of a fuse or other means commonly employed in practice. Lead azide, however, exhibits greater stability to heat and requires about twice as high a temperature to initiate detonation as does fulminate of mercury. The flash-point, that is, the lowest temperature which is just sufiicient to effect detonation of lead azide is about 330 (3., while the flash-point of fulminate of mercury is only about 160 C. Consequently. the application of lead azide as a primary initiating explosive is limited, for ignition is not assured by the methods commonly employed in practice. Thus itis evident that with respect to those properties in which fulminate of mercury is deficient, the azides excel and also that the chief point in favor of fulminate, its ease of ignition, is lacking in the azides.

Because of the above described conditions, it is highly desirable to provide a detonator charge which will embody the merits of the azides, and in which the deficiencies of the azides, (i. e., the high temperature required to initiate detonation) will be supplied by fulminate of mercury. Presumably, such a detonator charge would result from a mixture of fulminate with an azide. A review of the history of detonating explosives, however, reveals the fact that such a proposition has been suggested in 1911 (U. S. Patent No. 1,128,394.)

The reason that, after a period of ten years or more, the commercial and technical. practicability of such a proposition has not been demonstrated is as follows:

Different metals or alloys which are suitable for detonator casings or shells in most cases react oppositely with fulminate of mercury and lead azide so that as a rule a shell material which is satisfactory for one compound is highly unsatisfactory'for the other. For instance, fulminate of mercury can be used in copper shells, but, due to electrolytic or chemical action, it effects a rapid corrosion of zinc or aluminum shells. Similarly, lead azide may be used in aluminum shells, but cannot be used in copper shells because, in contact with copper, lead azide forms a dangerously sensitive copper azide. Thus it is evident that a mixture of these two compounds cannot be used in shells made of certain non-sparking metals, such as copper and aluminum, because the metal which Would be suitable for the one compound would be attacked by the other.

The above explanation is fully confirmed by experiments and by the fact that there is now being marketed a tetryl detonator, primed with lead azide, which, in turn, is covered with a third charge of an easilyignitible substance, other than fulminate of mercury, all of which is contained in an aluminum shell. Therefore, it would appear that all hopes of utilizing a mere mixture of fulminate and an azide had been abandoned.

Through experimentation, I have discovered that a certain metal salt of hydrazoic acid, other than lead azide, and which has heretofore been considered impractical for technical application, may be mixed with fulminate of mercury, with or without the addition of potassium chlorate, producing the desired results. found suitable for this purpose is the mercurous salt of hydrazoic acid.

Although the mercury salts of hydrazoic acid have been considered too dangerous to have practical importance I have found that the mercurous compound, in contradistinction to the mercuric azide, can be made by methods which will produce a comparative- 1y safe product. Mercurous azide is admirably suited for admixture with mercury fulminate because, in the first place, both compounds being salts of the same metal may be mixed without danger of chemical action, and in the second place. there is no appreciable action between such a mixture and shells which would be suitable for fulminate detonators. Throughout extensive experimentation I have found that the mercurous compound, in (.*ontradistinction to lead azide. does not form the super sensitive copper azide. Even in a moist atmosphere of carbon dioxide. copper is not appreciably attacked by mercurous azide, while. under similar conditions, lead azide very rapidly gives rise to the dangerous copper compound. The secret of this chemical inactivity of mercurous azide has two possible explanations, either of which may be dependent on the other.

1. The comparative positions of the metals involved. in the electro-motive series.

2. The comparatim solubilities of mercurous azide and lead azide in water.

The azide which I have sass Aluminum *+'1.04L0 Lead **+0.12 Copper 0.51 Mercury 0.80

* Neumann, Zeitshrift fur Physik, chemie 14, 22.).

** Noyes & Sherill, Principles of Chemistry, 1. 164.

It is also a well known fact that no metal can displace another metal from a salt unless water or other solvent be present.

Therefore the relative solubilities of two' difficultly soluble salts should furnish an index of their comparative reactivity with respect to a metal. I have found by actual experiments that mercurous azide is soluble in water at ordinary temperature to the extent of 0.03 grams per liter, while lead azide, under the same conditions, is soluble to the extent of 0.38 grams per liter. 'A small amount of water is almost unavoidably present in a detonator charge, remaining from a previously wet'condition of the ingredients, or from being supplied fromjhe moisture in the air, or both. The factthat lead azide is more than twelve times as soluble as mercurous azide is also in accord with the much greater tendency of lead azide tohave its metal displaced by certain other metals, such as copper.

The action of carbonic acid must also be considered. Carbon dioxide is present in the atmosphere. In. combination with. water it forms carbonic acid, which may act upon the azide with the liberation of the gaseous hydrazoic acid, which in turn may act upon the copper of the shell. with the formation of-the dangerous copper azide. The above figures show that mercurous azide is almost insoluble. Thorough and exhaustive tests 1n an atmosphere of carbon dioxide and moisture have shownthat copper or gilding metal shells with mercurous azide do not form this dangerous compound in a detectable amount, even over a long period of time. Lead azide, on the other hand, under the same comparative conditions quickly forms a deposit of this super-sensitive compound.

Further, under the influence of moisture and carbon dioxide. lead azide may be converted to a non-explosive mass, while, under the same conditions, mercurous azide is not noticeably affected. It is well known that ordinary air contains moisture and carbon dioxide and that mine air often contains even greater amounts.

In additionv to being Wholly practical from a standpoint of stability, I have found that from a standpoint of detonating efiiciency, the admixtures of small quantities of mercurous azide with fuhninate of mercury, produces most gratifying results. By extensive experimentation I have also found that the advantageous effects of such mixtures hold equally true when the mixtures include suitable proportions of po' tassium chlorate. The addition of potassium chlorate to the primary detonating composition in detonators is a well known and common procedure. These advantages may be summarized as follows.

1. The brisance or detonating value is greatly increased. The inner capsule, which is essential in a mercury fulminate-tetryl detonator, may be dispensed with, and a smaller priming charge used effectively.

2. Such mixtures are practically unaffeoted by moisture, whereas mercury fulminate or mercury fulminate-potassium chlorate alone are easily and quickly made ineffective by moisture.

3. Detonators charged with such mixtures are unimpaired by pressures at which fulminate of mercury or fulminate of vmercury-potassium chlorate mixtures befulminate, the flash point of various mixtures being practically identical with that of fulminate of mercury. Having described in detail the principles involved in my invention, I will now give specific examples which illustrate its application.

(1) A charge of 1.000 grams of 90-10 fulminate-mercurous azide mixture is charged and pressed into a copper or gilding metal shell.

(2) A charge of 1.000 gram of 8020 mercury fulminate-mercurous azide mixture is charged and pressed into a copper or gilding metal shell. Q

(3) A main charge of 0.50 gram of TN. T., tetryl, or other nitro aromatic explosive is charged and pressed into a copper or gilding metal shell. This main charge isprimed with a charge of 0.30 gram of an 80'20 fulminate of mercury-mercurous azide gilding metal shell.

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(4) A main charge of 0.50 gram of tetryl is charged and pressed into a copper or This main charge is primed with 0.30 gram of a mixture which consists of 80 parts fulminate of mercury, 10 parts of mercurous azide, and 10 parts of potassium chlorate.

While I have given specific examples of the use of mixturesof fulminate of mercury and mercurous azide in detonator compositions, it is to be understood that my invention is not limited to any particular detonator composition or to any specific methods of use in blasting caps or other means of initiating detonation, but that I desire to claim in the broadest manner the use of mixtures of fulminate of mercury and mercurous azide, with or without the addition of other ingredients.

While I have mentioned T. N. T. or tetryl as a main detonator charge combined with a priming charge of fulminate and mercurous azide other compositions may be used in lieu of the T. N. T., such, for example, as hexanitrodiphenylamine, with or without potassium chlorate or other oxidizing agent.

Having described my invention, what I An inner capsule is -not re- ,claim is 1. A detonator charge containing fulc minate ofmercury and mercurous azide.

2. A detonator charge containing fulminate of mercury, mercurous azide and an oxidizing agent.

3. A detonator charge comprising a priming charge of a mixture of mercurous azide and fulminate .of mercury, in conjunctionwith a suitable secondary charge.

4. A detonator charge comprlsing a primin charge of a mixture of mercurous azide, fu lminate of mercury and potassium chlorate, and a suitable secondary charge.

5. A detonator charge containing fulminate of mercury, mercurous azide, and potassium chlorate. i

6. A detonator charge containing fulminate of mercury, mercurous azide, potassium chlorate, and T. N. T.

In testimony whereof I aflix my signature in the presence of two witnesses.

BENNETT GROTTA. 

